Levels of measurement

• Nominal scale - A scale used to label variables that have no quantitative values
• Ordinal scale - A scale used to label variables that have a natural order, but no quantifiable difference between values
• Interval scale - A scale used to label variables that have a natural order and a quantifiable difference between values, but no “true zero” value
• Ratio scale - A scale used to label variables that have a natural order, a quantifiable difference between values, and a “true zero” value.